1. Field of the Invention
The present invention relates to an X-ray diagnostic apparatus with a computed tomography device of the type having an X-ray tube, which is fastened to a gantry ring and which emits a fan-shaped effective beam, and an opposed radiation receiver, which consists of a row of single detectors, each of which forms an electrical signal corresponding to the received radiation intensity.
2. Description of the Prior Art
German Utility Model 295 21 308 discloses an X-ray examination system with a computed tomography device and other receiving devices relevant to X-ray technology in which components of the system can be used jointly in connection with the computed tomography device and the other receiving devices.
In a computed tomography device of this type, an image of the irradiated slice of the examination subject is reconstructed from the output signals of the individual detectors obtained at various irradiation directions. Digital radiographs can also be generated in a shadow-image mode by the additionally provided X-ray device. To do this, however, the gantry of the computed tomography device must be pushed to the side so that the image pick-up by the additional X-ray device can proceed undisturbed.
U.S. Pat. No. 5,293,416 describes a computed tomography device with a curved CT detector in which an additional, stationary detector array for the creation of X-ray shadow images is provided. This additional detector array is arranged perpendicularly to the plane formed by the curved CT detector, i.e., it is arranged in the direction of the axis of rotation of the X-ray tube. A diaphragm which directs a fan-shaped X-ray onto the detector array for every position of the X-ray tube is provided in the beam path. CT exposures and X-ray shadow images can not occur simultaneously in this apparatus either, since at least the diaphragm must be pushed into the beam path of the X-ray tube.
U.S. Pat. No. 5,604,778 teaches a computed tomography device for spiral scanning which has a number of X-ray tubes, which are attached to the gantry ring, and a stationary annular CT detector row, or a number of CT detector rows which are fastened to the gantry ring, so that an improved and faster spiral scanning can occur. X-ray shadow images can not be produced with this apparatus.